Class definition syntax in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a class named Car.

Python

class [1]:
    pass

Drag options to blanks, or click blank then click option'

ACar

Bcar

Cvehicle

DCarClass

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase names for classes.

Adding parentheses after the class name when not inheriting.

The class name should be Car with a capital C to follow Python naming conventions.

2fill in blank

medium

Complete the code to add an __init__ method that takes self and color as parameters.

Python

class Car:
    def [1](self, color):
        self.color = color

Drag options to blanks, or click blank then click option'

A__init__

Bstart

Cinitialize

Dconstructor

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name like 'initialize' or 'constructor' which are not Python special methods.

Forgetting the double underscores.

The special method to initialize a class in Python is called __init__.

3fill in blank

hard

Fix the error in the method definition to correctly define a method named describe that takes only self.

Python

class Car:
    def describe([1]):
        print(f"This car is {self.color}.")

Drag options to blanks, or click blank then click option'

Acar

Bthis

Cself

Dcls

Attempts:

3 left

💡 Hint

Common Mistakes

Using other names like 'this' or 'cls' which are not correct for instance methods.

Omitting the parameter entirely.

The first parameter of instance methods must be self to refer to the object.

4fill in blank

hard

Fill both blanks to create a method named paint that changes the car's color to a new color passed as new_color.

Python

class Car:
    def [1](self, [2]):
        self.color = new_color

Drag options to blanks, or click blank then click option'

Apaint

Bcolor

Cnew_color

Dchange

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name different from the one assigned to self.color.

Using a method name that does not describe the action.

The method name should be paint and the parameter for the new color should be new_color.

5fill in blank

hard

Fill all three blanks to define a class Person with an __init__ method that takes self, name, and age, and assigns them to instance variables.

Python

class [1]:
    def [2](self, name, age):
        self.[3] = name
        self.age = age

Drag options to blanks, or click blank then click option'

APerson

B__init__

Cname

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect method names for the constructor.

Assigning to a different instance variable name than the parameter.

The class name is Person, the constructor method is __init__, and the instance variable for the name is name.

Practice

1. What keyword is used to define a class in Python?

easy

A. def

B. class

C. function

D. object

Solution

1. Step 1: Identify the keyword for class definition

   In Python, the keyword class is used to start a class definition.

2. Step 2: Differentiate from function and other keywords

   def defines functions, function and object are not Python keywords for class definition.

3. Final Answer:

   class -> Option B

4. Quick Check:

   Class keyword = class [OK]

Hint: Remember: classes start with 'class' keyword [OK]

Common Mistakes:

• Using def instead of class
• Confusing function keyword with class
• Trying to use object keyword

2. Which of the following is the correct syntax to define a class named Car?

easy

A. class Car:

B. class Car()

C. def Car():

D. class Car[]:

Solution

1. Step 1: Check class header syntax

   Python allows defining a class with or without parentheses if no base class is specified. So class Car: is correct.

2. Step 2: Identify incorrect options

   def Car(): defines a function, not a class. class Car() is valid syntax but less common; however, it requires a colon at the end. class Car[]: is invalid syntax.

3. Final Answer:

   class Car: -> Option A

4. Quick Check:

   Class header ends with colon, no brackets [OK]

Hint: Class header ends with colon, no brackets needed [OK]

Common Mistakes:

• Using def instead of class
• Adding square brackets [] in class header
• Omitting colon at end

3. What will be the output of this code?

class Dog:
    def __init__(self, name):
        self.name = name
    def bark(self):
        return f"{self.name} says Woof!"

my_dog = Dog("Buddy")
print(my_dog.bark())

medium

A. Dog says Woof!

B. Woof!

C. Buddy says Woof!

D. Error: missing self parameter

Solution

1. Step 1: Understand the __init__ method

   The __init__ method sets self.name to "Buddy" when my_dog is created.

2. Step 2: Analyze the bark method output

   The bark method returns a string using self.name, so it returns "Buddy says Woof!".

3. Final Answer:

   Buddy says Woof! -> Option C

4. Quick Check:

   Method uses self.name = Buddy [OK]

Hint: Methods use self to access object data [OK]

Common Mistakes:

• Ignoring self and expecting just 'Woof!'
• Confusing class name with instance name
• Forgetting to pass name argument

4. Find the error in this class definition:

class Person:
    def __init__(name):
        self.name = name

p = Person("Alice")

medium

A. self.name should be name.name

B. Missing colon after class name

C. Incorrect object creation syntax

D. Missing self parameter in __init__ method

Solution

1. Step 1: Check __init__ method parameters

   The first parameter of instance methods must be self. Here, __init__ lacks self.

2. Step 2: Confirm other syntax correctness

   Class header has colon, object creation syntax is correct, and self.name assignment is proper.

3. Final Answer:

   Missing self parameter in __init__ method -> Option D

4. Quick Check:

   Instance methods need self as first parameter [OK]

Hint: Always include self as first method parameter [OK]

Common Mistakes:

• Omitting self in methods
• Forgetting colon after class name
• Misusing self in attribute assignment

5. You want to create a class Book that stores title and author. Which is the best way to define the __init__ method to set these attributes?

hard

A. def __init__(self, title, author):
self.title = title
self.author = author

B. def __init__(title, author):
self.title = title
self.author = author

C. def __init__(self):
title = None
author = None

D. def __init__(self, title, author):
title = self.title
author = self.author

Solution

1. Step 1: Define __init__ with self and parameters

   The method must have self as first parameter, then title and author to receive values.

2. Step 2: Assign parameters to object attributes

   Use self.title = title and self.author = author to store values in the object.

3. Final Answer:

   def __init__(self, title, author): self.title = title self.author = author -> Option A

4. Quick Check:

   Init method sets attributes using self [OK]

Hint: Use self.param = param to store values in __init__ [OK]

Common Mistakes:

• Omitting self parameter
• Assigning attributes backwards
• Not passing parameters to __init__